After seven weeks of testimony, the trial of former New England mobster Frank Salemme – nicknamed “Cadillac Frank” -- is winding down. Jurors will hear closing arguments from the prosecution and the defense on Monday. Salemme is accused of murdering Boston nightclub owner Stephen DiSarro. To prove the case, federal prosecutors have called several ex-mafiosos to the stand. WGBH Radio’s Isaiah Thompson has been covering the trial at Boston's Moakley Federal Courthouse. He discussed the case and its background with WGBH's All Things Considered host Barbara Howard. The following transcript has been edited for clarity.

Barbara Howard: So these guys are not new to headlines?

Isaiah Thompson: That's right. I mean, a lot of the witnesses in this trial, especially the more prominent witnesses, have testified in prior cases, have been in the headlines - sometimes as criminals, sometimes as cooperating witnesses. And this is really over decades.

Barbara Howard: This trial represents, sort of, the last gasp of the old mafioso in the Boston area.

Isaiah Thompson: I think that's right. And it also represents, sort of, the last messy remnants of really decades of problematic and somewhat tortured relationships between the feds - prosecutors, the FBI - and organized crime.

Barbara Howard: And you have to remember that John Connolly, who plays a role in this, was an FBI agent who ended up going to prison for helping Whitey Bulger. And here he is again.

Isaiah Thompson: Yeah, that's right. Frank Salemme, the defendant now, testified against John Connolly. Frank Salemme was a cooperating witness with the government, he was on the government side. In that case, he was actually in witness protection when the warrant was issued for his arrest. We see someone who was a criminal, who became a "good guy" for the government - well, now he's the defendant. Now he's the accused.

Barbara Howard: It keeps crossing back and forth. And of course in that trial John Connolly was convicted, in part, for helping Whitey Bulger when he went on the lam. He tipped him off that he was about to be arrested. That's when he disappeared for all those years.

Isaiah Thompson: Yeah, that's right. And you know, another sort of bizarre crossing of streams here: the key witness in this trial against Frank Salemme was none other than Stephen Flemmi, who was Whitey Bulger's right-hand man, who was a member of the Winter Hill Gang. He was up on the witness stand in this trial testifying against Salemme for five days.

Barbara Howard: Several years ago some of these "bad guys" came forward and showed the authorities where bodies were literally buried, south of Boston, on a beach. But this particular body of this nightclub owner didn't surface until later, and that's what is triggering this case.

Isaiah Thompson: That's right. Stephen DiSarro's body wasn't found until 2016. Mr. DiSarro had been missing ostensibly since 1993, presumed dead. But I think part of what's also happening is that you have a number of aging former criminals who I think are more willing than they were in prior years to come forward and testify. Because I think they probably feel they don't have a lot to lose, and they're trying to bargain for better lives if they can. I think you have people who were once mob members, mafia members, Winter Hill Gang members, saying, 'Look, I've got to at least try to have a decent life for the rest of my life,' and are more willing to come forward and cooperate.

Barbara Howard: Of course the Winter Hill Gang being Whitey Bulger's old gang.

Isaiah Thompson: Whitey Bulger's old gang, that's right.

Barbara Howard: So if they're coming from prison, what makes their testimony credible?

Isaiah Thompson: That is a great question. And essentially the defense in this case - the lawyers for Frank Salemme and for his co-defendant Paul Weadick, who's also accused of participating in the murder - the defense lawyers basically told the jury, 'Look, you're going to hear from a bunch of people who are known criminals, are known liars.' In some cases, they literally have been convicted of perjury, or pleaded guilty to perjury. ... And what's more, they have incentive to lie, because all of the ex-mob members who testified in this case have made deals with prosecutors in one way or another. Stephen Flemmi, the key witness to this case - who's the only alleged eyewitness to the murder itself - he was able to avoid the death penalty by agreeing to cooperate with prosecutors. Not just in this case, but in several cases.

Barbara Howard: What's easily lost as we are covering these trials - because it sounds like a made-for-TV-movie, these mafia types - but there were real people. These were Bostonians and people around Boston whose lives were deeply affected by these crimes.

Isaiah Thompson: That's absolutely right. And the first witness we heard from in this case was Pamela DiSarro, the wife of Stephen DiSarro. And it was a real reminder of what that family has gone through. Pamela DiSarro testified to the morning in 1993 that she woke up early to see her husband leave the house, get in a car. She never saw her husband again. And that family, they've waited more than 25 years for closure and for justice.

Barbara Howard: We'll see what happens next week. Thanks for coming in, Isaiah.

Isaiah Thompson: Thanks for having me.

Barbara Howard: That's WGBH Radio's Isaiah Thompson. He has been covering the trial of ex-mobster Frank Salemme. Closing arguments are scheduled for Monday. This is All Things Considered.